Geographically-diverse redundant servers over optical connections with managed path differential delay

Abstract

The present disclosure relates to systems and methods for geographically-diverse redundant servers and the like interconnected via wavelength division multiplexed (WDM) systems with managed path differential delay of the WDM systems. The present disclosure provides transport systems and methods incorporating absolute time references, such as global positioning system (GPS) time references and/or the like, and selective buildout delays, such as first-in, first-out (FIFO) buildout delays and/or the like. In one exemplary embodiment, the transport systems and methods of the present invention are used in conjunction with the International Business Machine Corporation (IBM) Geographically-Dispersed Parallel Sysplex (GDPS) integrated, automated application and data availability solution to meet and/or exceed the associated 10 microseconds transmit/receive path differential delay requirement. Other comparable uses are also contemplated herein, as will be obvious to those of ordinary skill in the art.

What is claimed is: 
     
       1. A geographically diverse server system, comprising:
 a first server; 
 a second server; 
 an optical system interconnecting the first server and the second server over a transmit path and a receive path between the first server and the second server; 
 wherein each of the first server and the second server is configured to:
 measure differential delay between the transmit path and the receive path; and 
 compensate the differential delay between the transmit path and the receive path; 
 
 wherein the optical system comprises a first network element connected to the first server and a second network element connected to the second server, and wherein the first network element is connected to the second network element through an optical network; 
 a first external time reference connected to the first network element; and 
 a second external time reference connected to the second network element; 
 wherein the first network element is configured to calculate first transmit path delay and first receive path delay utilizing the first external time reference and wherein the second network element is configured to calculate second transmit path delay and second receive path delay utilizing the second external time reference. 
 
     
     
       2. The geographically diverse server system of  claim 1 , further comprising:
 a first buffer at the first network element configured to implement a delay based on the first transmit path delay and the first receive path delay by buffering; and 
 a second buffer at the second network element configured to implement a delay based on the second transmit path delay and the second receive path delay by buffering. 
 
     
     
       3. The geographically diverse server system of  claim 1 , further comprising:
 a first storage area network connected to the first server; and 
 a second storage area network connected to the second server. 
 
     
     
       4. The geographically diverse server system of  claim 1 , wherein the first server and the second server communicate one or more signals between one another via the optical system. 
     
     
       5. The geographically diverse server system of  claim 4 , wherein the one or more signals comprise Fibre Connection (FICON). 
     
     
       6. The geographically diverse server system of  claim 4 , wherein the one or more signals comprise Fibre Channel (FC). 
     
     
       7. The geographically diverse server system of  claim 4 , wherein the one or more signals comprise InterSystem Channel-3 (ISC-3) Compatibility Mode. 
     
     
       8. The geographically diverse server system of  claim 4 , wherein the one or more signals comprise InterSystem Channel-3 (ISC-3) Peer Mode. 
     
     
       9. The geographically diverse server system of  claim 4 , wherein the one or more signals comprise InterSystem Channel-3 (ISC-3) Peer Mode with Server Time Protocol messaging. 
     
     
       10. The geographically diverse server system of  claim 1 , wherein the first server and the second server form a Geographically-Dispersed Parallel Sysplex (GDPS) from IBM Corporation. 
     
     
       11. A Geographically-Dispersed Parallel Sysplex (GDPS) system, comprising:
 a first location (A); 
 a second location (Z); and 
 interconnecting means between the first location and the second location, wherein the interconnecting means comprises a path differential measurement and management tool; 
 wherein the path differential measurement and management tool is configured to:
 measure A to Z delay over the interconnecting means; 
 measure Z to A delay over the interconnecting means; 
 if measured A to Z delay<measured Z to A delay, implement a delay between A and Z equal to measured Z to A delay minus measured A to Z delay; and 
 if measured Z to A delay<measured A to Z delay, implement a delay between Z and A equal to measured A to Z delay minus measured Z to A delay. 
 
 
     
     
       12. A method, comprising:
 between two servers A and Z, measuring an A to Z delay and measuring a Z to A delay at the two servers A and Z; 
 selectively compensating for delay based on the measured A to Z delay and the measured Z to A delay at the two servers A and Z; 
 if measured A to Z delay<measured Z to A delay, implementing a delay between A and Z equal to measured Z to A delay minus measured A to Z delay; and 
 if measured Z to A delay<measured A to Z delay, implementing a delay between Z and A equal to measured A to Z delay minus measured Z to A delay. 
 
     
     
       13. The method of  claim 12 , further comprising:
 receiving an external time reference at both the servers A and Z; and 
 utilizing the external time reference in the measuring the A to Z delay and measuring the Z to A delay.